Merge branch 'for-4.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - a new PIDs controller is added.  It turns out that PIDs are actually
   an independent resource from kmem due to the limited PID space.

 - more core preparations for the v2 interface.  Once cpu side interface
   is settled, it should be ready for lifting the devel mask.
   for-4.3-unified-base was temporarily branched so that other trees
   (block) can pull cgroup core changes that blkcg changes depend on.

 - a non-critical idr_preload usage bug fix.

* 'for-4.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: pids: fix invalid get/put usage
  cgroup: introduce cgroup_subsys->legacy_name
  cgroup: don't print subsystems for the default hierarchy
  cgroup: make cftype->private a unsigned long
  cgroup: export cgrp_dfl_root
  cgroup: define controller file conventions
  cgroup: fix idr_preload usage
  cgroup: add documentation for the PIDs controller
  cgroup: implement the PIDs subsystem
  cgroup: allow a cgroup subsystem to reject a fork

1 files changed, 15 insertions, 2 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 2b1a61cddc19..03aa2e6de7a4 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1246,6 +1246,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 {
         int retval;
         struct task_struct *p;
+        void *cgrp_ss_priv[CGROUP_CANFORK_COUNT] = {};
 
         if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS))
                 return ERR_PTR(-EINVAL);
@@ -1518,6 +1519,16 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         p->task_works = NULL;
 
         /*
+         * Ensure that the cgroup subsystem policies allow the new process to be
+         * forked. It should be noted the the new process's css_set can be changed
+         * between here and cgroup_post_fork() if an organisation operation is in
+         * progress.
+         */
+        retval = cgroup_can_fork(p, cgrp_ss_priv);
+        if (retval)
+                goto bad_fork_free_pid;
+
+        /*
          * Make it visible to the rest of the system, but dont wake it up yet.
          * Need tasklist lock for parent etc handling!
          */
@@ -1553,7 +1564,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
                 spin_unlock(&current->sighand->siglock);
                 write_unlock_irq(&tasklist_lock);
                 retval = -ERESTARTNOINTR;
-                goto bad_fork_free_pid;
+                goto bad_fork_cancel_cgroup;
         }
 
         if (likely(p->pid)) {
@@ -1595,7 +1606,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         write_unlock_irq(&tasklist_lock);
 
         proc_fork_connector(p);
-        cgroup_post_fork(p);
+        cgroup_post_fork(p, cgrp_ss_priv);
         if (clone_flags & CLONE_THREAD)
                 threadgroup_change_end(current);
         perf_event_fork(p);
@@ -1605,6 +1616,8 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 
         return p;
 
+bad_fork_cancel_cgroup:
+        cgroup_cancel_fork(p, cgrp_ss_priv);
 bad_fork_free_pid:
         if (pid != &init_struct_pid)
                 free_pid(pid);